The present invention relates to a supported catalyst useful for the (co)-polymerization of olefins and particularly ethylene under high temperatures and pressures and to the process of (co)-polymerizing olefins and particularly ethylene in the presence of the supported catalyst.
The present invention especially relates to the polymerization of ethylene in the presence of the improved supported catalyst at temperatures higher than 125.degree. C. without the need for deashing.
The polymerization of ethylene at high pressure (1000-3000 bar) and high temperature (150.degree.-340.degree. C.) in the presence of a peroxide initiation capable of producing free radicals, has been known and used commercially for many years.
A process to polymerize ethylene at a relatively low temperature (70.degree.-100.degree. C.) and low pressure, not greater than 35 bar, by using a catalyst of the Ziegler-type, such as, for example, titanium trichloride and an alkyl aluminum compound, has also been known and used commercially for many years.
More recently, catalyst components comprising magnesium chloride supported titanium tetrachloride have been found to be highly useful for polymerization of olefins.
Many of these prior art high-efficiency Ziegler catalysts as described in the plethora of patent literature, have high productivities at a temperature range between 60.degree. and 100.degree. C. However, such high efficiency Ziegler catalysts normally rapidly decay at polymerization temperatures higher than 100.degree. C., making them unsuitable for use under high pressure--high temperature conditions. Furthermore, these catalysts present a pumpability problem in high pressure systems as a result of their large particle size.
Recently, a number of patents directed towards the polymerization of olefins under high temperatures and pressures have been published. Typical of the patents are U.S. Pat. No. 3,969,332 and British Pat. No. 1,441,115, each assigned to Ethylene Plastique and U.S. Pat. No. 4,263,170, U.K. patent application No. 2,002,399 A and European patent application No. 0070749 Al. Each of the catalysts disclosed in these patents, although useful for the polymerization at high temperatures, evidence some disadvantages, such as, for example, the large size of the catalyst particles. Large catalyst size is a disadvantage with respect to pumping ease and settling problems at high temperature-pressure polymerizations. Another disadvantage of some of the catalysts disclosed in the above patents is that the catalytic activity is poor, requiring removal of catalyst residues from the resulting polymer.
It would be advantageous to develop a catalyst which can be usefully employed for the production of high density polyethylene or linear low density polyethylene under high temperatures and high pressures, which catalyst would combine the properties of high activity, thereby eliminating the need for deashing the polymer product, a short half-life of about less than 2 minutes, thereby eliminating or reducing the need for quenching agents as the polymer product egresses from the reactor, and the average particle size of the catalyst is approximately 5 microns, thereby facilitating catalyst pumping without settling problems at high pressures and without damaging pump seals.
Recently, a catalyst component useful for the polymerization of propylene and alpha-olefins under Ziegler-type conventional polymerization conditions i.e., at temperatures less than about 100.degree. C., and at conventional pressures have been described in U.S. Pat. No. 4,347,158 of Dart Industries, Inc. The catalyst described therein comprises a support base which is milled with an inorganic Lewis acid and electron donors and combined with an active transition metal compound.